Sodium thiosulfate pentahydrate has numerous industrial applications including such uses as removing chlorine from solutions, bleaching paper pulp, and extracting silver from ores. It is also used as a fixer in photography, a mordant in dyeing and printing textiles, and a pharmaceutical ingredient. Even though thousands of metric tons of sodium thiosulfate pentahydrate are produced annually, only a few hundred kilograms are utilized pharmaceutically for the production of sodium thiosulfate injection as currently indicated as a treatment for cyanide poisoning or for the production of a lotion containing sodium thiosulfate pentahydrate for the treatment of tinea versicolor. It has been recently reported that sodium thiosulfate pentahydrate is an effective treatment for calciphylaxis (Ackermann et al., Archives of Dermatology 2007, 143(10): 1336-1337). It has also been reported that sodium thiosulfate pentahydrate is an effective treatment for vascular calcification (O'Neill, Kidney International 2008, 74(11): 1376-1378). It has been reported that sodium thiosulfate pentahydrate is an effective treatment to prevent platinum-induced ototoxicity and nephrotoxicity that is associated with the use of platinum-containing chemotherapeutic agents (Skinner, Current Opinions in Oncology 1995, 7(4): 310-315).
The manufacture of pharmaceutical products in the United States is regulated by the Food and Drug Administration (FDA). Since the passage of the Federal Food Drug and Cosmetic Act in 1938, the FDA has required new pharmaceutical products and their corresponding active ingredients to be manufactured in accordance with the exacting requirements of “pharmaceutical grade” Good Manufacturing Practices as detailed in the United States Code of Federal Regulations 21 CFR 211. Because of the relatively small quantity of sodium thiosulfate pentahydrate that is currently used to formulate pharmaceutical products, no raw material supplier presently manufactures sodium thiosulfate pentahydrate in accordance with “pharmaceutical grade” Good Manufacturing Practices.
In addition to regulating manufacturing practices, the FDA establishes stringent quality specifications for each new pharmaceutical product and its corresponding active ingredients. A pharmaceutical product is classified as “new” if it was introduced to the market after the passage of the Food Drug and Cosmetic Act in 1938. As mandated in this Act, the FDA requires a new pharmaceutical product and its active ingredients to be manufactured in accordance with “pharmaceutical grade” Good Manufacturing Practices and to meet applicable quality specifications. When the Food Drug and Cosmetic Act was enacted in 1938, pharmaceuticals that were already on the market were classified as “grandfathered drugs” and were permitted to remain on the market without formal FDA approval if the product and its labeling remain unchanged. Any change to the product or its labeling would cause the “grandfathered drug” to become a “new” drug that is subject to FDA-imposed regulations and quality standards. Currently available sodium thiosulfate pentahydrate injection that is labeled solely for use as a treatment of cyanide poisoning and sodium thiosulfate pentahydrate-containing lotion that is labeled solely for use as a treatment of tinea versicolor are “grandfathered medications”. Consequently, the product formulations and corresponding quality specifications have remain unchanged for decades.
In anticipation of the receipt of a New Drug Application for a sodium thiosulfate pentahydrate-containing pharmaceutical product, the FDA recently announced that sodium thiosulfate pentahydrate raw material for a new pharmaceutical product must be manufactured in accordance with “pharmaceutical grade” Good Manufacturing Practices and must conform to a new set of quality specifications. This new set of quality specifications is more expansive and stringent than the existing quality specifications. Currently available sodium thiosulfate pentahydrate raw material does not meet the new set of FDA quality standards and is unsuitable for use in the formulation of a new pharmaceutical product. Consequently, there is a clear and unmet need for purified sodium thiosulfate pentahydrate raw material that is manufactured in accordance with “pharmaceutical grade” Good Manufacturing Practices and that meets the new set of quality specifications in order to translate recent sodium thiosulfate pentahydrate-related research discoveries into FDA-approved clinical therapies.
Another hurdle in developing pharmaceutical grade sodium thiosulfate pentahydrate is the lack of an effective analytical method to determine total non-purgeable organic carbon in a sodium thiosulfate pentahydrate-containing sample, which is one of the new FDA-imposed quality standards. The conventional method for total non-purgeable organic carbon determination requires that any inorganic carbon must be removed before measuring the organic carbon content in a sample. This is typically achieved by adding acid. At low pH, the inorganic carbon and volatile organic carbon are converted to carbon dioxide, which is then purged from the sample. The sample is then routed to a combustion chamber with a catalyst and a temperature of approximately 680° C. to convert any remaining non-purgeable (non-volatile) organic carbon to carbon dioxide. The quantity of carbon dioxide thus produced is then determined using an infrared detector. However, this conventional method cannot be used to analyze a sodium thiosulfate pentahydrate-containing sample. When exposed to acid, sodium thiosulfate pentahydrate degrades to sulfur which can precipitate during the analysis. Salt from sodium thiosulfate pentahydrate may also precipitate during the analysis. Precipitants can damage laboratory equipment and interfere with analysis. Therefore, there is also a need for an analytical method for determining total non-purgeable organic carbon in a sodium thiosulfate pentahydrate-containing sample.